Amp Build: Marshall 18 Watt (Trinity 18)

etzeppy

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When it comes to amps, I've always been a Fender guy. I have been interested in something British and toyed with getting a Marshall Class 5. I have built a few pedals and I'm not completely terrible with a soldering iron. I got brave and decided to build my own Marshall 18 watt amp.

I opted to kit the parts for convenience and selected Trinity as the source. The Trinity 18 design is a stock Normal channel with the Tremolo channel converted to TMB. The modified channel is offered with several different voicings; I chose their "Plexi" layout.

I love that mini Bluesbreaker look so I went with the combo chassis. I will wait until it works to determine if I want to buy a cabinet.

I have had the components for a few months but was intimidated to get going on it. With some days off for the holidays, I got brave a few days ago and dove in. Here is the pile of parts.



You start by mounting the transformers, tube sockets, front panel, and switches. You then wire up the power transformer, AC source, and attach the heater wires to the sockets. Those are easy words to say, but it was pretty slow work. I didn't get a good shot of the heater wires during the build. They are twisted and run along the bottom lip of the chassis. I want them as far away from the circuit wires as possible to reduce noise.



Fire it up it and check for correct voltage. The light is on and no smoke!



Heater voltages all look good.

To Be Continued!
 

etzeppy

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The next step is to assemble the turret board per the Trinity 18 Plexi layout. I went very slowly and tested every resistor before placement. I hope it is all correct.



Many hours later, here is the almost-complete board with the input and output wires attached. I am missing one capacitor (omitted from my parts bag) and still need to attach the output wires for the Plexi volume boost.



I got into a zone and plowed through most of the off-board wiring in one long session. I should have paused for a few pics to show the tight spaces and mess of wires I was dealing with. I started with the pots and moved left to right. On the tube sockets, I wired right (V1) to left (V5). The impedance switch and speaker outputs finished up most of the wiring. Here is the nearly complete build.







I still need to wire up the shielded input wires and the Plexi volume boost switch. The layout called for a toggle between V2 & V3 (see the hole). It doesn't seem very usable in that location. I opted for a push/pull toggle on the volume pot but need to plan out the best wiring path.

I was stupid and forgot that I didn't have the EL84 power tubes I need. I ordered a pair just before Christmas and hope they get here soon. I also need that missing 220uF cap for the Normal channel. I'll probably complete the wiring and give this thing a complete review for errors, while waiting on the additional parts.

It might be several days before the next update.
 

Bobby Mahogany

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You're an inspiration to us all!
:D

What a bummer that missing cap!
Can't wait to see it kicking and reading your review.
:thumb:
 

Heddok

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Looks very very good. I'm really curious to hear how it sounds. I've spent a lot of time researching the Trinity kits. So if you could post your impressions it would be great.

Nice clean build you're doing
 

warprider

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Fantastic! I'm gonna follow your lead, albeit with KLD 18w TMB HR (reverb) kit for all of $124. It's semi assembled already.
476428916_1-kld-firetone-18hr-18-watt-handwired-head.jpg

For $225 I could have just purchased the head but I'm wanting to build one.

I have a gutted VHT 12" cab that it's going into. I'm waiting on the chassis now. Before deciding on this I got a good deal on the tubes so those are ready to go.

Looking forward to updates here.
 

cherrysunburst00

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Fantastic! I'm gonna follow your lead, albeit with KLD 18w TMB HR (reverb) kit for all of $124. It's semi assembled already.
View attachment 349668
For $225 I could have just purchased the head but I'm wanting to build one.

I have a gutted VHT 12" cab that it's going into. I'm waiting on the chassis now. Before deciding on this I got a good deal on the tubes so those are ready to go.

Looking forward to updates here.
May I ask where you got your kit from?
 

etzeppy

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The parts are in. I have the missing capacitor but where does this 100K resistor go? It's like that extra screw when you assumable furniture.



Looks like that 100K resistor is needed. I left it off the gain pot. Oh the fun of sucking off solder and redoing wiring in tight spots. I did that and added the shielded cable run for the gain control. That stuff is hard to work with. I also wired up the volume boost switch as a push/pull on the volume pot. Now on to the input jacks.



Another slight snag. This Trinity kit only came with 3 feet of shielded cable. That is at least 1.5 ft short for gain, hi/low TMB inputs, and hi/low Normal inputsl. I contacted Trinity support; 3 feet is the correct amount for the kit but they also acknowledged that it is not really enough. Not sure how that happens, but they are sending me 2 more feet. They also indicated that the allotment for the kit will be increased. In the mean time, I will wire up the TMB channel and just wait on the Normal.

Wiring up of the input jacks was challenging and took a lot of patient work. I barely had enough cable for Gain and TMB inputs and felt a little sloppy with the routing. However, it's all done. Time to recheck everything and get ready for power up. Scary......

 
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etzeppy

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Power up starts with only the rectifier tube and some measurements for proper voltage. A glowing tube and no smoke....so far so good.




Install the rest of the tubes, load it with a speaker, and power up again in Stand By mode. Look at that glow!



I'm feeling pretty good at this point. Now, flip the stand by and hope for the best. No fuse pop, no crazy noises. Time to measure expected voltages on the tube pins. Panic! Smoke on or near one of the power tubes. I shut it all down, waited a few minutes, and tried again. Just a tiny bit of smoke near the same power tube which then dissipates. It must have been a little isolation on a hot pin, oil on the glass (although I was careful not handle directly), some contact cleaner. At the advise of Eurotubes, I always give the pins a little spray before seating.

Anyway....it all looks okay and the voltages are in the ballpark. Let's put a cable to the input, give it some volume, and touch the end. No sound at all. What did I do wrong? I was just about to retrace the input wiring, then it hit me. I need some gain too. This is a master vol variation on the TMB channel. There it is...glorious hum! I plugged in a guitar and the damn thing works. Best I can tell, all of the tone stack controls function. It does sound really bright though. It's brand new Celestion Greenback speaker, no cabinet, and no grill cloth. Perhaps bright is expected in that circumstance. I intend to recheck the circuit just to make sure. I will do that tomorrow. Time for beer.

 
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etzeppy

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Last time I posted on build progress, I was waiting on more shielded cable for the Normal input, and also planned on adding a Voltage Regulation Module (VRM). The VRM is a Trinity design that allows adjustment the main DC supply voltage (from the rectifier) from the nominal 350V all the way down to approximately 115V. The purpose is to lower the output power of the amp while maintaining reasonable tone.

So here we go. I really, really hate working with shielded cable. On one end you peel away the shield and protect it with shrink wrap. On the input end, you twist the shielding and connect to ground. It doesn't help that everything is really tight and hard to work with near the input jacks.




For the VRM, I had to undo some my previous work (which I also hate). Apparently as you lower the voltage, there can be some DC voltage bleed into the guitar's volume pot. That causes noise as you work the knob. The solution is a DC blocking cap. You also need to move the standard 1M input resistor to the V1 input side because of the new cap. This all translates to....reworking the input at both ends. After an hour of planning and struggling, the V1 end turns into this.


With the inputs fixed up on both ends, it's time to build and install the VRM. It takes the place of the ON/OFF switch, using a switched pot. The completed VRM circuit is pretty compact, but has to fit into a tight space.



After a little more work, it turns into this. Not quite right. The instructions showed both leads of the light on same side of the switch. I didn't catch that and just did it. It was an easy fix.


Here is the finished chassis, all ready to go.


I'm waiting on a cabinet from Sourmash. It is supposed to ship Monday! For now I am running it into a Cannabis Rex speaker in this Princeton Reverb cab.


I am really happy with this little guy so far. The VRM was worth the trouble and allows reasonable bedroom volume. It gets fizzy turned all the way down, but sounds "right" with just a little more voltage. The Plexi channel sounds just like it should, with a great range from clean to OD...really killer tone. I have not had a chance to run it with real volume yet.

I built a Box of Rock pedal a while back but never found a good use for it. It works so well with this amp. I am glad I have it.



Hopefully the cab will be in by the weekend and I can finish this thing up. It has been a lot of work and a lot of hours. I think I could do it in half the time now. There was a definite learning curve. However, I'm no amp expert or master with a soldering iron. The project is doable with some patience and minimal skills.
 
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sonar

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Great thread! Thanks for sharing.

When I first started thinking about building amps I was all about the 18 watt, but somewhere took a hard turn and went all in on Fender. A Vibro Champ, Princeton Reverb, Tweed Deluxe, 6G15 reverb unit and an AB165 Bassman restore later I've yet to build a Marshall style amp.

I really don't need another amp, but your thread sure does tempt me.
 

Case24

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Great build. I just built the same kit only as a head two weeks ago. This was my second Trinity build. I built a 5E3 Tweed Deluxe from them and posted the build on here 8 years ago. It’s still going strong to this day. I can vouch that Trinity Amps make a great kit.
 

etzeppy

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Great build. I just built the same kit only as a head two weeks ago. This was my second Trinity build. I built a 5E3 Tweed Deluxe from them and posted the build on here 8 years ago. It’s still going strong to this day. I can vouch that Trinity Amps make a great kit.
Did you do the VRM option in yours?
 

akuster777

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Excellent work! I built a ceriatone 18 watt tremolo kit, also sourmash cab, and I love it. Enjoy your tonez!
 




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